When he revealed on-air last week a stunning extortion plot borne of his relationships with female staffers, "Late Show" host David Letterman refused to name his lovers. The act earned him some praise and sympathy.

But his plan to protect those women seems to have backfired. Many past and present female staffers have suddenly been put in an unwanted spotlight, harassed by tabloid phone calls and paparazzi. Letterman acknowledged this on his show Monday night, issuing an apology to his entire staff.

He also apologized publicly to his wife Regina Lasko, herself a former Letterman staffer. Two former female employees have come forward. Another, whom sources say may have triggered the extortion plot, has remained quiet. Here's what we know about the three of them.

The woman who appears to be at the center of the scandal is Letterman's former assistant, Stephanie Birkitt. Frequently a participant in on-air "Late Show" sketches over the years, Birkitt was the live-in girlfriend of alleged Letterman extortionist Robert "Joe" Halderman, a producer for CBS' "48 Hours."According to the New York Post, Birkitt recently moved out of Halderman's Norwalk, Connecticut home where she'd been living with him since 2004.

When she moved out, Birkitt reportedly left behind her personal diary containing detailed notes about her relationship with Letterman. It was later discovered by Halderman, a fact confirmed by a law enforcement official .

Birkitt's diary also allegedly revealed that she was still involved with Letterman after she began dating Halderman. That revelation may have set Halderman off as Birkitt had previously insisted that the relationship between she and Letterman was strictly "platonic," and that she was his "best friend."

As of this writing, Birkitt has not commented publicly about the scandal, though her father did tell the press that she's going through a "rough time" right now.